This application relates to a liner for a vane pump, wherein a pre-pressurization opening is positioned to eliminate cross-flow between suction and discharge pressure chambers.
Vane pumps are known and typically include a rotor rotating within a liner. A cam surface within the liner is positioned eccentrically relative to a rotational axis of the rotor. Vanes extend radially inwardly and outwardly of the rotor, and in contact with the cam surface. Movement of the vanes along the cam surface causes the vanes to move inwardly and outwardly and move a pump fluid from a suction or inlet to an outlet through pump chambers defined between the vanes.
Thus, when the pump chamber communicates with the discharge window opening, an immediate increase in pressure creates rapid decrease in air volume.
Pre-pressurization has been utilized in the past to provide a “step change” in the overall volume reduction and pressure increase. Pre-pressurization occurs by introducing pressurized fluid into inter vane chambers prior to the chambers communicating with the full discharge window opening. With this, there is a step down to an intermediate volume and increase in pressure.
In the existing art, this pre-pressurization opening communicates with a pump chamber prior to an upstream vane making contact with the cam surface downstream of a suction opening. In this way, the pre-pressurization discharge fluid communicates back toward the suction pressure chamber.
This can result in reduced pumping efficiency.